Photosensitizing molding and coating compositions with benzoin-silyl-esters

ABSTRACT

The invention relates to possibly Alpha -substituted benzoinsilyl-esters which are useful photosensitizers for the photopolymerization of polymerizable compounds or compound mixtures including mixtures of unsaturated polyesters and copolymerizable monomeric compounds.

United States Patent Fuhr et al.

[54] PHOTOSENSITIZING MOLDING AND COATING COMPOSITIONS WITHBENZOIN-SILYL-ESTERS [72] Inventors: Karl Fuhr; Hugo Vernaleken;Hans-Georg Heine, all of Krefeld; Hans Rudolph, Krefeld-Bockum; HermannSchnell, Krefeld- Uerdingen, all of Germany Farbenfabriken BayerAktiengesellschaft, Leverkusen, Germany [73] Assignee:

[30] Foreign Application Priority Data Nov. 6, 1968 Germany ..P 18 07297.4

[52] US. Cl. ..204/l59.15, 204/l59.23, 260/4483 R 51 May 23, 1972 [5 1]Int. Cl ..C08d l/00, C08f H16 [58] FieldofSearch ..204/l59.23, 159.15;260/448.8 R

[56] References Cited UNITED STATES PATENTS 3,582,487 6/1971 Fuhr et al...204/l59.23

Primary Examiner-J0hn C. Bleutge Assistant Examiner-Richard B. TurerAttorney-Connolly and Hutz [5 7] ABSTRACT The invention relates topossibly a-substituted benzoin-silylesters which are usefulphotosensitizers for the photopolymerization of polymerizable compoundsor compound mixtures including mixtures of unsaturated polyesters andcopolymerizable monomeric compounds.

7 Claims, No Drawings PHOTOSENSITIZING MOLDING AND COATINGcopolvmerizable monomeric compounds can be used particu- COMPOSITIONSWITH BENZOIN-SILYL-ESTERS larly advantageously, and here unsaturatedpolyesters are, as usual, to be understood as polycondensation productsof a,

CROSS REFERENCE To RELATED APPLICATION unsaturated dicarboxylic acidssuch as maleic acid and fumae- This application is a division ofapplication Ser. No. 5 ic acid, with P V Such 35 l glycol and p P367,938, fil d Oct 20 9 9 1,2. A part of the unsaturated acids can bereplaced by satu- The object f the invention are bcnzoin silyl csters ff rated acids, such as for example phthalic acid. Further modifimulacations are possible through building-in monobasic acids and R l0monohydric alcohols. So-called air-drying moulding composim( (|fiy tionswhich apart from the radicals of a,/8-unsaturated dicarboxylic acidsalso contain B,-y-unsaturated ether radicals, 0 I either as aconstituent of further components of the mixture,

M50103 can alsobeused.

By copolymerizable monomeric compounds, there are to be understood theunsaturated compounds which are customary in polyester technology havingvinyl groups which are optionally substituted in the aposition or allvlgroups substituted in the B-position, preferably styrene.

wherein R represents hydrogen, lower alkyl or alkenyl having one toabout four C-atoms, aralkyl or phenyl, R represents lower alkyl havingone to about four C-atoms, preferably methyl, and R" and R, which may beidentical or different, represent hydrogen, halogen, lower alkyl havingone to about four C-atoms, or methoxy. The photopolymerizable compoundsor mixtures can be sta- Typical examples of such benzoin-silyl-estersare: bilized by the addition of usual inhibitors, for examplelMimi:1-l.rin|vl.hyl-silyl-vstvr... Boiling poinmn 118 C Melting point77 a-Muthyllwiizoiibtri|nvtliylsilyl-vstvr. Boiling point 120 C Meltingpoint 32 C.

Boiling pointnm 110-113 CH DB 1.5377.

a-lmmiyllmnzoin-trimothylsilyl-estvr..t Boiling pointum 155158 C Meltingpoint 43-44" C. 4,4-(lim0thyl-benzoin-trimetliyl-silyl-estor... Boilingpointom 140 C no 1.5412. 4,4-dimothoxy-benzoin-trimethyl-silyl-esterBoiling point 180 C 11 3 1.5598.

A further object of the invention is the use of the new comhydroquinone,in the known amounts. Polymerization pounds as photosensitizers in thephotopolymerization of subcatalysts, for example peroxides, canoptionally also be constances or substance mixtures which containpolymerizable jointly employed in the usual amount. In conjunction withthe double bonds. 35 use of ketone hydroperoxides, metal compounds, forexample A large number of sulphur-containing and halogen-containcobaltnaphthenate, can be added for acceleration of ing compounds have beenmentioned amongst others in the complete cure. In this case the storagestability of the literature as compounds which initiate and acceleratephotopolymerizable compositions is admittedly lowered. lt isphotopolymerizations. Further substances which have been thereforeadvisable when manufacturing lacquer coatings to recommended are benzoin(US. Pat. No. 2,367,661) and work in accordance with the so-calledactive primer method in some benzoin derivatives, such as certaina-substituted which the coating composition is applied to aperoxide-conbenzoins US. Pat. No. 2,722,512) and benzoin-ethers ofpritaining layer which is applied beforehand to the substrate. maryalcohols (US. Pat. No. 2,448,828) and French Pat. No. It is particularlyadvantageous to employ the new benzoins 1,450,589). in those coatingcompositions to which paraffin or wax or wax- None of these compoundshas be n l t fin in ustri l like substances are added, which float tothe surface at the acceptance. As causes for this, there should bementioned the start of the polymerization and prevent the inhibitingaction of excessively low reactivity and the inadequate storagestability atmospheric oxygen.

the h the polyl'henzable compouhfjs these In order to protectlight-sensitive substrates, for example photoschsmzersg but m P also theQ of the light timbers, small amounts of customary ultra-violet absor- PY F csRcclahy after Prolohgcd stofage m h bers can be added to themoulding and coating compositions .Agamst thls the new cofnpoundsfi mcofnphnson to the without the reactivity being significantly impaired.Furtherhnhehm know most acme henzom denvatwes h as more, small amountsof customarv carriers and fillers as well benzoin-methyl-ether andbenzoin-ethyl-ether, cause particuas agents which confer thixotropv suchas glass fibcrs larly slight discolorations in polymers when thepolymers are exposed to daylight, for a prolonged period, and in partalso zi gg g i fiz g i ggh and talcum can be present dunng the possessexcellent reactivity and storage stability in the dark.

The benzoin-alkylsilyl-esters are appropriately employed in amounts offrom about 0.1 to about 5 percent by weight, preferably from about 0.5to about 2.5 percent by weight, either individually or as a mixture withone another.

Suitable polymerizable compounds are all substances of which thecarbon-carbon double bonds are activated by, for example, halogen atomsor carbonyl, cyanide, carboxyl, ester, amide, ether or aryl groups aswell as carbon double bonds 55 and carbon triple bonds. As examplesthere may be men- As radiation sources for carrying out thephotopolymerization it is possible to use natural sunlight or artificialradiators with an emission in the range of about 250 to about 500 ;1.,preferably from about 300 to about 400 a. Mercury vapor lamps, xenonlamps and tungsten lamps are for example suitable. The compositionsaccording to the invention also cure rapidly to colorless mouldings andcoatings under the ultraviolet and visible radiation of low energyfluorescent lamps with an emission of rays of about 300 to about 5 80 u.

tioned: styrene, vinyl toluene, divinyl benzene, vinyl acetate, Whenmanufacturing mouldings from the sensitized comvinyl chloride,vinylidene chloride, vinyl methyl ketone, acrylpositions, it provesparticularly advantageous that the comic and methacrylic acid, estersthereof such as the methyl, positions can be cured by appropriatelymetered irradiation ethyl and allvl ester, their amides and nitriles,and other allyl without a significant heat effect, as a result of whichlarger esters, such as allyl acetate, phthalic acid diallyl ester andmouldings can also be obtained free of cracks. in the absence phosphoricacid triallyl ester, and mixtures of such comof peroxides and metalaccelerators the cure can optionally pounds. also be interrupted byplacing the material in the dark and can Moulding and coatingcompositions from mixtures, stabilbe completed at any desired time afterstorage of the ized in the usual manner, of unsaturated polyesters andprepolymersthus obtained.

The new compounds can be manufactured in a manner which is in itselfknown by reaction of benzoins with substances which split offtrialkylsilyl groups, for example trimethyl-silyl chloride,hexamethyldisilazane and N-trimethylsilylacetamide, optionally in polarsolvents such as pyridine, dimethylsulphoxide and dimethylformamide.

Benzoin-trimethylsilyl-ester can be manufactured in accordance with thefollowing instruction: a solution of 50 g of benzoin (0.236 mol) in 100ml of hexamethyldisilazane is heated for 1 hour to the boil withexclusion of moisture after the addition of two drops of concentratedsulphuric acid. During this time the sump temperature is 125C. Duringthe course of the reaction ammonia is split off. Thereafter the excesshexamethyldisilazane is distilled off under normal pressure and theremainder is distilled 01f in vacuo. A double distillation ofbenzoin-trimethylsilyl-ester follows in order to purify the crudeproduct. The boiling point of the benzointrimethylsilyl-ester is boilingpoint 1 18C and the yield is 55 g, equal to 81 percent.

a-Methylbenzoin-trimeth lsilvl-ester can for example be manufactured inaccordance with the following instruction: a solution of 31.5 g ofa-methylbenzoin (0.139 mol) in 190 ml of hexamethyldisilazane is heatedfor 7 hours to the boil with exclusion of moisture, after addition of 2drops of concentrated sulphuric acid. During this time the sumptemperature is 125C. Ammonia is split off during the course of thereactron.

Thereafter the excess hexamethyldisilazane is distilled off under normalpressure and the remainder is distilled off in vacuo. A distillation ofthe a-methylbenzoin-trimethylsilylester follows in order to purify thecrude product. The boiling point of thea-methylbenzoin-trimethylsilyl-ester is boiling point 120125C and theyield is 35.3 g, equal to 85 percent.

a-Ethylbenzoin-trimethylsilyl-ester can for example be manufactured inaccordance with the following instruction: a mixture of 4.60 g ofa-ethylbenzoin (0.019 mol) and 3.67 g of N-trimethylsilylacetamide isheated for 3 hours to 140C with exclusion of moisture. Thereafter thereaction mixture is cooled to room temperature and taken up in drytoluene, and the acetamide which is insoluble in toluene is filteredoff. ln order to isolate the a-ethylbenzoin-trimethvlsilyl-ester thetoluene is distilled off at normal pressure and the remainder isdistilled off in vacuo. A distillation of thea-ethyl-benzointrimethylsilyl-ester follows in order to purify the crudeproduct. The boiling point of the a-ethylbenzoin-trimethylsilyl-ester isat boiling point 1l0113C and the yield is 4.00 g, equal to 67 percent.

EXAMPLE 1 g of extracted and freshly distilled acrylic acid methyl esterare mixed with 0.1 g of two known sensitizers and one sensitizeraccording to the invention.

Illumination is carried out with a mercury vapor high pressure lamp(Philips HPK 125 W/L) through quartz glass in a water bath at 24C, at adistance of 10 cm. Here the solution of the sensitizer in the monomer iscontained in a quartz glass of internal diameter 1.7 cm under a nitrogenatmosphere. The time of illumination is 2 A minutes. Immediately afterthe illumination the quartz glass is introduced into an acetone/solidcarbon dioxide mixture in order to prevent a thermal polymerization. Thesolution of the polymer in the monomer and the solid polymerconstituents which are present on the inside of the quartz glasses onthe side facing the mercury vapor high pressure lamp are introduced intoa small round flask by means of small quantities of a solvent (methylenechloride).

Thereafter unpolymerized monomeric constituents and the solvent aredistilled off in a rotating evaporator. After drying in a vacuum dryingcabinet to constant weight at 60C, the amount of polymer is determined.

Table 1 contains a summary of the amounts of poly( acrylic acid methylester) obtained with various sensitizers.

TABLE 1 If an initiator is not present, the amount of polymer is lessthan 0.1 percent.

EXAMPLE 2 An unsaturated polyester manufactured by condensation of 152parts by weight of maleic anhydride, 141 parts by weight of phthalicanhydride and 195 parts by weight of propanediol- 1,2 is mixed with0.045 parts by weight of hydroquinone and dissolved in styrene to give a65 percent by weight solution.

Two parts by weight of two different known photosensitizers on the onehand and of three different photosensitizers according to the inventionon the other hand are added to parts by weight at a time of this form inwhich the resin is supplied and the mixture is stored with exclusion oflight at 60C until it gels. Table 2 contains the sensitizers employedand the values of the storage stability at 60C.

TABLE 2 Sensitizer Storage stability at 60 C.

Benzoin Benzoin-cthyl-ether a-Methylbenzoin-trimethylsilyl-esteraEthylbenzoin-trimethylsilyl-ester a-Phenylbenzoin-trimethylsilyl-esterless than 1 day less than 1 day more than 10 days more than 10 days morethan 10 days EXAMPLE 3 Twenty parts by weight of styrene, one part byweight of a 10 percent by weight solution of paraffin (melting point 5253C) in toluene as well as, on the one hand, known photosensitizers and,on the other hand, photosensitizers according to the invention inequimolar amounts are mixed into 100 parts by weight at a time of theform in which the resin is supplied, described in example 2. Thesolutions thus obtained are applied to glass plates by means of a filmspreader (500 u) and illuminated with the radiation from a fluorescentlamp (Osram L 40 W70-1) at a distance of 5 cm.

Table 3 contains the times for the paraffin to float to the surface andthe times for reaching a pencil hardness 6 l-l.

In contrast to benzoin and benzoin-ethyl-ether the new compounds aredistinguished by the fact that they give practically no cause fordiscolorations both during polymerization and also on subsequent storageof the polymers under the influence of light.

EXAMPLE 4 One hundred parts by weight of the form in which the resin issupplied, described in Example 2, are mixed with 20 parts by weight ofstyrene, one part by weight of a percent by weight solution of paraffin(melting point 52-53C) in toluene and two parts by weight ofa-methylbenzointrimethylsilyl-ester and additionally with variousperoxides, metal containing compounds and ultraviolet absorbers. Fivehundred p. thick layers of these solutions are applied to glass platesby means of a film spreader and exposed to the radiation of thefluorescent lamp described, at a distance of 5 cm. The times for theparaffin to float to the surface and the times until a pencil hardness 6H is reached are contained in Table 2 Cobalt naphthenate solution (20%strength in toluene) 0.05 a-Cyano-a-( 4-methoxyphenvl methacrylic acidbutyl ester 14 We claim:

1. In the process of photopolymerizing a moulding and coatingcomposition comprising (a) an unsaturated polyester of ana,B-unsaturated dicarboxylic acid and a polyol and b) a copolymerizablemonomer, the improvement comprising employing as sensitizer abenzoin-silyl ester of the fonnula R!!! R RI! ll 6 slam wherein Rrepresents hydrogen, lower alkyl or alkenvl having one to about fourC-atoms, aralkyl or phenyl, R represents lower alkyl having one to aboutfour C-atoms and R and R', which may be identical or different,represent hydrogen, halogen, lower alkyl having one to about fourC-atoms, or methoxy.

2. The process of claim 1 wherein R and R and R' are hydrogen and R ismethyl.

3. The process of claim 1 herein R and R are methyl and R" and R arehydrogen.

4. The process of claim 1 wherein R is ethyl, R is methyl and R" and Rare hydrogen.

5. The process of claim 1 wherein R is allyl or phenvl, R is methyl andR" and R are hydrogen.

6. The process of claim 1 wherein R is hydrogen and R and RandRaremethl.

7. The process 0 claim 1 wherein R is hydrogen, R is methyl and R and Ris methoxy.

2. The process of claim 1 wherein R and R'''' and R'''''' are hydrogenand R'' is methyl.
 3. The process of claim 1 herein R and R'' are methyland R'''' and R'''''' are hydrogen.
 4. The process of claim 1 wherein Ris ethyl, R'' is methyl and R'''' and R'''''' are hydrogen.
 5. Theprocess of claim 1 wherein R is allyl or phenyl, R'' is methyl and R''''and R'''''' are hydrogen.
 6. The process of claim 1 wherein R ishydrogen and R'' and R'''' and R'''''' are methyl.
 7. The process ofclaim 1 wherein R is hydrogen, R'' is methyl and R'''' and R'''''' ismethoxy.